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How do disease-causing mutations arise and how are they maintained in populations?.
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How do disease-causing mutations arise and how are they maintained in populations?
Balanced polymorphism: the heterozygote enjoys an advantage that has allowed selection for the gene, making the homozygous condition common. The prime example is sickle cell disease, in which the heterozygote enjoys immunity to malaria. Cystic fibrosis, Tay Sach’s, Gaucher's, and probably others are probably also balanced polymorphisms.
“People who are exposed to HIV but somehow don't become infected may owe their lives to survivors of Europe's bubonic plague epidemic in the 1300s,” according to a report in the May 1998 issue of the American Journal of Human Genetics.
The plague killed between one-quarter and one-third of Europe's population between 1347 and 1350.
About 14% of people of Scandinavian descent have this mutation. However, the defective CCRC mutation is rare in people of African or East Asian ancestry. Figure source: Scientific American at http://www.sciam.com/ 0997issue/0997obrienbox5.html
Human genetic diversity HLA blood groups ABO Blood Groups Lactose Insufficiency
Antigens Diseases • A Syphilis • Smallpox • B Infantile • diarrhea • Typhoid fever • (not typhus) • O Bubonic Plague
The Human Genome Diversity Project (the "HGD Project") is an international project that seeks to understand the diversity and unity of the entire human species.
The definition of a separate human "population" is not precise, but, using language as the primary criterion, there are between 4,000 and 8,000 distinct human populations around the world.
Iceland: A genetically homogeneous population with detailed medical records going back more than 60 years.
“I find it disgusting that people can make such huge amounts of money by breaking ethical rules.” says psychiatrist Peter Hauksson, who is among the 25 percent of Icelanders who object to Stefansson’s plan.